1. Field of the Invention
The present invention relates generally to a keypad apparatus used for an electronic device. More particularly, the present invention relates to a keypad apparatus using a Light Guide Plate (LGP) to provide a thinner and simpler structure.
2. Description of the Related Art
FIG. 1 is a cross-sectional view illustrating a conventional LGP keypad apparatus. Referring now to FIG. 1, a light guide plate (LGP) 50 including a plurality of reflector patterns 90 is disposed over a Printed Circuit Board (PCB) 70 and a dome sheet 60, and a rubber sheet 30 having pressing protrusions 40 is disposed over the LGP 50. A film sheet 20 covers the top of the rubber sheet 30, and key buttons 10 are adhered to the film sheet 20. A light source 80 for irradiating light to the light guide plate 50 is disposed on the PCB 70, facing one side of the LGP 50.
FIGS. 3A and 3B illustrate a conventional portable wireless terminal which is slidable in a horizontal or vertical direction. As shown in the example in FIG. 3A, if a keypad 220 is open by pushing up a display unit 210 having its longest surface in the horizontal direction, a keypad with alphabet letters such as ‘U’, ‘I’, ‘O’ and ‘P’ printed thereon appears. As shown in FIG. 3B, if the keypad 220 is open in the vertical direction, a keypad 225 with Arabic numerals printed thereon appears. An LGP keypad shown in FIG. 2 is conventionally used to realize the above keypad. The LGP keypad apparatus of FIG. 2 is also manufactured as follows. A second light guide plate 140 having pressing protrusions 150 including reflector patterns 145 and a first light guide plate 130 with a plurality of reflector patterns 135 are disposed over a PCB 170 and a dome sheet 160, and a rubber sheet 120 and a film sheet 115 are disposed over the top of the first light guide plate 130. Key buttons 110 are adhered to the film sheet 115. A first light source 180 irradiates light only to the first light guide plate 130, and a second light source 190 irradiates light only to the second light guide plate 140. In this structure, by selectively activating the first light source 180 or the second light source 190, the alphabet letters, for example, ‘I’, ‘O’ and ‘P’ printed on the first light guide plate 130 can be displayed on the keypad, or the Arabic numerals, for example, ‘3’, ‘6’ and ‘9’ printed on the second light guide plate 140 can be displayed on the keypad. Since this conventional keypad apparatus for an electronic device is complex in structure, it is thick and has a large number of parts, causing an increase in manufacturing cost and processing time.